Chapter 12- Circulation
Vocabulary
Vein/ venule
Artery/arteriole
Vasoconstriction/vasodilatation
Blood pressure
osmotic pressure
Heart
Atrium/ ventricle
Semilunar valves
cardiac cycle
Purkinje fibers
ECG/EKG
Hypertension
Atherosclerosis
Stroke
lymphatic system
capillary
pulse
aneurism
valve
systole/diastole
Sphygmomanometer
septum
SA/AV node
endocardium
pericardium
pulmonary circuit/systemic circuit
coronary artery disease /myocardial infarction
lymph nodes
Lecture Outline
Blood vessels
Pathway of blood
The heart
Cardiovascular health & disease
The lymphatic system
Learning objectives
 Name, in order, the types of vessels that carry blood as it flows from the heart through the body
and back to the heart.
 Define pulse and explain how to find the pulse.
 Explain how vasoconstriction and vasodilation regulate blood flow in arteries.
 List the mechanisms responsible for the exchange of materials across the capillary wall.
 Compare the structure of arteries, veins and capillaries and explain how these structures
facilitate the function of each type of vessel.
 Explain how blood is returned to the heart against the force of gravity.
 Describe the structure of the heart as a double pump.
 Describe the structure and function of the heart valves.
 Name each major vessel and chamber of the heart as blood flows from the left ventricle to the
left atrium.
 Describe control of the heartbeat.
 List three factors that determine blood pressure.
 Define hypertension and describe why it is life threatening.
 Describe how atherosclerosis develops and why it is dangerous.
 Explain the relationship between coronary artery disease, angina pectoris, and heart attack.
 List the functions of the lymphatic system and specifically of the lymph nodes.
 Compare the structure of lymphatic capillaries with vessels found in the circulatory system.
Intro and Blood vessels
The circulatory system is a closed loop which pumps blood it contains all around the body, providing
oxygen, nutrients, and defense, while removing wastes from the body’s cells
The circulatory system is made of blood vessels (veins, arteries, and capillaries) which hold the blood,
and the heart, which moves the blood within the system in a circular loop (actually 2 connected circular
loops, one going to the lungs and back to the heart, the other going to the body and then returning back
to the heart)
Arteries take blood away from the heart, to either the lungs or the body
Ateries have 3 layers- an outer layer comprised of connective tissue, an inner layer comprised of a single
layer of epithelial tissue, and a thick middle layer comprised primarily of contractile smooth muscle
The smooth muscle of arteries can contract, or be expanded, smoothing out waves of pressure sent
from the heart
Ateries branch into arterioles, whose smooth muscle layer, while thinner, had a strong influence on
blood pressure
Veins return blood from the body or lungs back to the heart
Like arteries, veins have 3 layers of tissue, however, since the blood in veins is not pressurized by the
force of the beating heart, the layer of smooth muscle tissue is much thinner
Veins have valves to make sure blood does not flow backward as it is not pushed by the heart
Veins hold the major reservoir of a person’s blood, and are found at the convergence of venules, smaller
veins which also contain valves
Capillaries are tiny, single-walled blood vessels where venules and arterioles meet
Capillaries are where nutrient and gas exchange occur, at the lungs and the body
Few cells are more than three cells away from a capillary which feeds them
Nutrients and gasses pass through the thin epithelial walls of capillaries driven either by diffusion, blood
pressure, or osmotic pressure
Precapillary sphincters control access of aterial blood to capillary beds
Because they are not pressurized, the blood in capillaries and veins moves much more slowly than the
blood in arteries
The pathway of blood
The lungs are where oxygen is picked up, and carbon dioxide is dropped off
Blood from the lungs, rich in oxygen, is brought back to the heart by the pulmonary veins into the left
atrium of the heart (pulmonary circuit)
The left ventricle pumps the oxygen-rich blood it receives from the left atrium and sends it through the
aorta to the arteries of the whole body
The blood passes through arterioles, and then into the capillary beds which permeate the body’s tissues,
where oxygen and nutrients are released to the body tissues, and carbon dioxide and other wastes are
removed by the blood (Systemic circuit)
Deoxygenated blood from body tissues is returned to venules, and then to veins, and finally back to the
right atrium of the heart
From the right atrium, blood is sent into the right ventricle, which pumps the blood back to the lungs to
release the body’s waste and pick up a new load of oxygen, completing the circuit
The human heart can pump blood in a complete circuit around the body back to its starting point in
about thirty seconds
The Heart
The heart is actually two muscular pumps, the right side and left side, comprised of four chambers:
Right atrium, Right ventricle, Left atrium, Left ventricle
The right side pumps blood moving in the pulmonary circuit, the left side moves blood in the systemic
circuit
Coronary circulation serves the heart muscle, as the heart cannot use the oxygen and nutrients from the
blood it directly pumps
The beating of the heart generates the systolic blood pressure by sending waves of blood through the
arteries with each beat
A sphygmomanometer can measure changes in blood pressure, giving readings for systolic and diastolic
blood pressure
The cardiac cycle, the sequence of muscle contractions of the four chambers of the heart, is controlled
by the Sinoatrial (SA) node, a bundle of specialized muscle tissue which can send out electrical impulses
Though hormones and the nervous system can send signals telling the heart to beat faster, the SA node
is independent of the nervous system and sends its impulses independently of signals from the rest of
the body
The impulses from the SA node are picked up by the AV node, and then passed on through the Purkinje
fibers, causing the ventricles to contract
An electrocardiogram, or EKG (or ECG) is a measure of the electrical activities of the heart
Cardiovascular health and disease
Irregular electrical activity of the heart can lead to arrhythmias, which can be life threatening and lead
to cardiac arrest
High blood pressure causes no major symptoms and is therefore called the silent killer
High blood pressure requires the heart to work harder with every stroke
Atherosclerosis is the accumulation of cholesterol plaque on the insides of artery walls
Atherosclerosis increases blood pressure, reduces the resiliency of the artery walls, reduces blood flow
to the tissues those arteries feed, and increases the risk of heart attack and/or stroke
Coronary artery disease is atherosclerosis in the coronary arteries, the arteries which feed the tissues of
the heart
When occluded arteries become completely blocked, often caused by a blood clot moving through the
blood vessels, the tissues fed by that artery die; if the artery is a coronary artery, this will result in a
myocardial infarction
The lymphatic system
The lymphatic system collects lymph, interstitial fluid which leaks from capillaries into the tissues
Filled with white blood cells, the lymph nodes of the lymphatic system fight infection
Lymphoid organs include the tonsils and the thymus gland, where T lymphocytes are matured